The present invention generally relates to gasket seals for fluids and, more particularly, the present invention has application in creating fluidic seals in the ink delivery systems for ink jet printing systems.
In general there are two types of gasket seals in use today to seal fluids within mechanical systemsxe2x80x94compressive seals and gland seals. A compressive seal is a flat gasket that is compressed between two mechanical parts. These seals are physically xe2x80x9csandwichedxe2x80x9d between the parts by a mechanical joint and typically use face seals between the gasket and each of the parts. A common example of a compressive seal is the head gasket on an internal combustion engine. On the other hand, a gland seal, such as an O-ring, is a seal that utilizes a mismatch in the size of two parts to create a compressive force for sealing. An example of a gland seal is an O-ring placed on a cylinder that is pressed into a hole. The mismatch between the diameter of the cylinder plus the annular thickness of the O-ring and the inside diameter of the hole compresses the O-ring and produces a seal.
The disadvantages of compressive seals are well known. Compressive seals must be continuously subjected to a compressive force, i.e., continuous loading. Further, the gasket itself over time takes on a xe2x80x9ccompression setxe2x80x9d which, in turn, causes the mechanical joints to loosen up. In addition, relaxation of the compressive force can cause the seal to leak.
Gland seals, as well, have their disadvantages. They are very difficult to incorporate into applications other than circular shapes. For any complex geometrical shape or for an elongate shape, i.e., a shape with a large aspect ratio, a compressive seal is typically used. Also, during the assembly of parts, gland seals are difficult to handle and since one gasket is required for each seal, the part counts are high.
Over-molding is a well known, two step, fabrication process in which a rigid substrate is first formed, typically by injection molding. Thereafter, in a second step a layer of elastomer is molded onto the substrate typically by thermoset or thermoplastic injection molding.
Two overmolding methods are commonly used. The first is used for overmolding onto rigid thermoplastics. In this process, a ridge thermoplastic piece is molded. A thermoplastic elastomer is then overmolded after a section of movable coring is retracted. The thermoplastic part may be required to endure high mold temperatures during the second step of this process.
The second method of overmolding is used to overmold thermoset elastomer onto either a rigid thermoset or thermoplastic piece. In this process, a rigid piece (thermoset or thermoplastic) is molded using traditional injection molding techniques. The part is then transferred to a second mold cavity wherein the thermoset elastomer is injected onto it. Again, the rigid piece may endure high mold temperatures during the overmold process.
In the past shaped layers of elastomer with under cuts and overhangs have been uncommon because when the part is removed, the mold either tears the elastomer overhang off the elastomer layer or tears the entire elastomer layer off the substrate. Secondly, it has been found that if the elastomer overhang is compressed during assembly, there has been difficulty in supporting it and preventing it from being squashed by the mechanical joint.
There is also a continuing need in manufacturing for parts that are lower cost, easier to handle, and require fewer critical tolerances. Further, there is a need for assembled components that have lower part counts and are easier to assemble. Lastly, there is an ongoing need for robust fluidic seals and ink conduits for the ink delivery systems in ink jet printing systems. In these printing systems the seals serve as both mechanical bonds for holding assemblies together and seals for containing ink.
Thus, it will be apparent from the foregoing that although there are some well known fluid sealing techniques and fluid conduit systems, there is still a need for an approach that combines the beneficial aspects of both gland seals and compressive seals.
Briefly and in general terms, an apparatus for producing a fluidic seal according to the present invention includes a rigid substrate having an elastomeric layer over-molded thereon and an elastomeric gland seal molded into the over-molded layer. Another aspect of the apparatus according to the invention includes a rigid host-part having a raised wall thereon, said host-part receives the elastomeric gland seal and compresses the gland seal with the raised wall.
Further, an apparatus for producing a fluid conduit according to the present invention comprises a rigid substrate having an elastomeric layer over-molded thereon; an elastomeric gland seal molded into the over-molded layer for producing a fluidic seal; and a rigid host-part having a raised wall thereon, said host-part receives the elastomeric gland seal and compresses the gland seal with the raised wall. The substrate, the gland seal, and the host-part define an enclosed region. The apparatus also includes a fluid inlet port and a fluid outlet port that communicate with the enclosed region.
Other aspects of the invention will become apparent from the following detailed description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the invention.